Rockwell hardness of pins of a certain type is known to have a mean value of 50 and a standard deviation of 1 2 a If the distribution is normal, what is the probability that the sample mean hardness for a random sample of 9 pins is at least 51 b Without assuming population normality, what is the (a...

Rockwell hardness of pins of a certain type is known to have a mean value of 50

Question:

Rockwell hardness of pins of a certain type is known to have a mean value of 50 and a standard deviation of 1.2.
a. If the is normal, what is the probability that the sample mean hardness for a random sample of 9 pins is at least 51?
b. Without assuming population normality, what is the (approximate) probability that the sample mean hardness for a random sample of 40 pins is at least 51?
Distribution
The word "distribution" has several meanings in the financial world, most of them pertaining to the payment of assets from a fund, account, or individual security to an investor or beneficiary. Retirement account distributions are among the most...